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A two player game over the intranet..

- by Santwana

Hi everybody.. I am a student of 3rd year engineering and only a novice in my programming skills. I need some help with my project.. I wish to develop a two player game to be played over the network (Intranet). I want to develop a simple website with a few html pages for this.My ideas for the project run as follows: 1.People can log in from different systems and check who ever is online on the network currently. the page also shows who is playing with whom. 2.If a person is interested in playing with a player who is currently online, he sends a request of which the other player is somehow notified( using a message or an alert on his profile page..) 3.If the player accepts the request, a game is started. This is exactly where I am clueless.. How can I make them play the game? I need to develop a turn based game with two players, eg chessboard.. how can I do this? The game has to be played live.. and it is time tracked. i need your help with coding the above.. the other features i wish to include are: 4.The game could not be abruptly terminated by any one if the users.The request to terminate the game should be sent to the other player first and only if he accepts can the game be terminated. Whoever wins the game would get a plus 10 on their credit and if he terminated he gets a minus 10. The credits remains constant even if he loses but the success percentage is reduced. 6.The player with highest winning percentage is projected as the player of the week on the home page and he can post a challenge to all others.. I only have an intermediate knowledge of core java and know the basics of Swing and Awt. I am not at all familiar with networking in java right now. I have 5 to 6 weeks of time for developing the project but I hope to learn the things before I start my project. i would prefer to use a lan to illustrate the project and I know only java,jsp,oracle,html and bit of xml to develop my proj. Also I wish to know if I can code this within 6 weeks, would it be too difficult or complicated? Please spare some time to tell me. Please.. please.. I need your suggestions and help.. thank you so much..

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Pure sine wave inverter

- by Nick

Not exactly programming (sorry) but I think it's pretty close and can be of interest to other programmers. I'm trying to setup a battery power station so that I can work from anywhere. I go surfing a lot and my idea is to be able to work from wherever I can park my car (given there's coverage). So, I'm getting a deep cycle battery, a 240V charger (I'm in Australia), and an inverter. At the back of my laptop it says 19V and 4.62A. From the people I've spoken to that means it consumes about 90W at most. So my inverter needs to be able to output about 100W. Most of them seem to be 200W and up so this shouldn't be a problem. I want to be able run my laptop for 10 hours (plus the 2 hours I get from the laptop battery) straight. According to the people I've spoken to and from what I gather online I need a battery that has the amp hours for my "amp draw". I have no idea how to calculate this but I've been guesstimating. Most deep cycle batteries seem to be classified using amp hours (Ah)... 35Ah, 50Ah, 75Ah, 100Ah, and so on. However the amp hours on those batteries is for a 240V and I seem to be using 19V. According to an expert I spoke to you'd need a 100Ah battery to power a 5A appliance at 240V for 10 hours (you only get about 50% useful power). That to me is 5A * 240V = 100Ah battery. So, naive as I might be I take 240V and divide that by my 19V and reach the conclusion that I can get away with a battery that's about 12 times smaller than that 100Ah. The expert told me I needed a 50Ah battery so that's probably what I'll be getting, but it would be interesting to know what I theoretically would need to power my laptop for 10 hours. As for charging the battery the expert I spoke to said I needed a 3-5A charger to be able to charge that 50Ah battery from flat to full in about 10 hours (I will just leave it plugged in over night). Now to my question. The expert said it's not a matter of "if" more like a guaranteed "when" my computer will stuff up if I don't use a "pure sine wave inverter". From what I gather the power that comes out of that battery is not as clean as the power we get in the socket at home. Apparently it's "square" and the one in the socket is nice and smooth. I've already got an inverter, but it's not "pure". Do I really need to buy the $200-300 pure sine wave inverter or can I get away with something else? Perhaps the laptop adapter that sits in the middle of my laptop power cable already fixes that wave to be nice and smooth? Thanks!

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Where are the function literals c++?

- by academicRobot

First of all, maybe literals is not the right term for this concept, but its the closest I could think of (not literals in the sense of functions as first class citizens). The idea is that when you make a conventional function call, it compiles to something like this: callq <immediate address> But if you make a function call using a function pointer, it compiles to something like this: mov <memory location>,%rax callq *%rax Which is all well and good. However, what if I'm writing a template library that requires a callback of some sort with a specified argument list and the user of the library is expected to know what function they want to call at compile time? Then I would like to write my template to accept a function literal as a template parameter. So, similar to template <int int_literal> struct my_template {...};` I'd like to write template <func_literal_t func_literal> struct my_template {...}; and have calls to func_literal within my_template compile to callq <immediate address>. Is there a facility in C++ for this, or a work around to achieve the same effect? If not, why not (e.g. some cataclysmic side effects)? How about C++0x or another language? Solutions that are not portable are fine. Solutions that include the use of member function pointers would be ideal. I'm not particularly interested in being told "You are a <socially unacceptable term for a person of low IQ>, just use function pointers/functors." This is a curiosity based question, and it seems that it might be useful in some (albeit limited) applications. It seems like this should be possible since function names are just placeholders for a (relative) memory address, so why not allow more liberal use (e.g. aliasing) of this placeholder. p.s. I use function pointers and functions objects all the the time and they are great. But this post got me thinking about the don't pay for what you don't use principle in relation to function calls, and it seems like forcing the use of function pointers or similar facility when the function is known at compile time is a violation of this principle, though a small one.

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circles and triangles problem

- by Faken

Hello everyone, I have an interesting problem here I've been trying to solve for the last little while: I have 3 circles on a 2D xy plane, each with the same known radius. I know the coordinates of each of the three centers (they are arbitrary and can be anywhere). What is the largest triangle that can be drawn such that each vertice of the triangle sits on a separate circle, what are the coordinates of those verticies? I've been looking at this problem for hours and asked a bunch of people but so far only one person has been able to suggest a plausible solution (though i have no way of proving it). The solution that we have come up with involves first creating a triangle about the three circle centers. Next we look at each circle individually and calculate the equation of a line that passes through the circle's center and is perpendicular to the opposite edge. We then calculate two intersection points of the circle. This is then done for the next two circles with a result of 6 points. We iterate over the 8 possible 3 point triangles that these 6 points create (the restriction is that each point of the big triangle must be on a separate circle) and find the maximum size. The results look reasonable (at least when drawn out on paper) and it passes the special case of when the centers of the circles all fall on a straight line (gives a known largest triangle). Unfortunate i have no way of proving this is correct or not. I'm wondering if anyone has encountered a problem similar to this and if so, how did you solve it? Note: I understand that this is mostly a math question and not programming, however it is going to be implemented in code and it must be optimized to run very fast and efficient. In fact, I already have the above solution in code and tested to be working, if you would like to take a look, please let me know, i chose not to post it because its all in vector form and pretty much impossible to figure out exactly what is going on (because it's been condensed to be more efficient). Lastly, yes this is for school work, though it is NOT a homework question/assignment/project. It's part of my graduate thesis (abet a very very small part, but still technically is part of it). Thanks for your help.

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php regex guitar tab (tabs or tablature, a type of music notation)

- by John

I am in the process of creating a guitar tab to rtttl (Ring Tone Text Transfer Language) converter in PHP. In order to prepare a guitar tab for rtttl conversion I first strip out all comments (comments noted by #- and ended with -#), I then have a few lines that set tempo, note the tunning and define multiple instruments (Tempo 120\nDefine Guitar 1\nDefine Bass 1, etc etc) which are stripped out of the tab and set aside for later use. Now I essentially have nothing left except the guitar tabs. Each tab is prefixed with it's instrument name in conjunction with the instrument name noted prior. Some times we have tabs for 2 separate instruments that are linked because they are to be played together, ie a Guitar and a Bass Guitar playing together. Example 1, Standard Guitar Tab: |Guitar 1 e|--------------3-------------------3------------| B|------------3---3---------------3---3----------| G|----------0-------0-----------0-------0--------| D|--------0-----------0-------0-----------0------| A|------2---------------2---2---------------2----| E|----3-------------------3-------------------3--| Example 2, Conjunction Tab: |Guitar 1 e|--------------3-------------------3------------| B|------------3---3---------------3---3----------| G|----------0-------0-----------0-------0--------| D|--------0-----------0-------0-----------0------| A|------2---------------2---2---------------2----| E|----3-------------------3-------------------3--| | | |Bass 1 G|----------0-------0-----------0-------0--------| D|--------2-----------2-------2-----------2------| A|------3---------------3---3---------------3----| E|----3-------------------3-------------------3--| I have considered other methods of identifying the tabs with no solid results. I am hoping that someone who does regular expressions could help me find a way to identify a single guitar tab and if possible also be able to match a tab with multiple instruments linked together. Once the tabs are in an array I will go through them one line at a time and convert them into rtttl lines (exploded at each new line "\n"). I do not want to separate the guitar tabs in the document via explode "\n\n" or something similar because it does not identify the guitar tab, rather, it is identifying the space between the tabs - not on the tabs themselves. I have been messing with this for about a week now and this is the only major hold up I have. Everything else is fairly simple. As of current, I have tried many variations of the regex pattern. Here is one of the most recent test samples: <?php $t = " |Guitar 1 e|--------------3-------------------3------------| B|------------3---3---------------3---3----------| G|----------0-------0-----------0-------0--------| D|--------0-----------0-------0-----------0------| A|------2---------------2---2---------------2----| E|----3-------------------3-------------------3--| |Guitar 1 e|--------------3-------------------3------------| B|------------3---3---------------3---3----------| G|----------0-------0-----------0-------0--------| D|--------0-----------0-------0-----------0------| A|------2---------------2---2---------------2----| E|----3-------------------3-------------------3--| | | |Bass 1 G|----------0-------0-----------0-------0--------| D|--------2-----------2-------2-----------2------| A|------3---------------3---3---------------3----| E|----3-------------------3-------------------3--| "; preg_match_all("/^.*?(\\|).*?(\\|)/is",$t,$p); print_r($p); ?> It is also worth noting that inside the tabs, where the dashes and #'s are, you may also have any variation of letters, numbers and punctuation. The beginning of each line marks the tuning of each string with one of the following case insensitive: a,a#,b,c,c#,d,d#,e,f,f#,g or g. Thanks in advance for help with this most difficult problem.

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issues regarding UAC prompt

- by peter

I want to implement a UAC prompt for an application in visualc++ the operating system is 32bit x7460(2processor) Windowsserver 2008 the exe is myproject.exe through manifest.. Here for testing i wl build the application in Windows XP OS and copy the exe in to system containg the Windowsserver 2008 machine and replace it So what i did is i added a manifest like this name of that is myproject.exe.manifest My project has 3 folders like Headerfile,Resourcefile and Source file.I added this manifest(myproject.exe.manifest) in the Sourcefile folder containing other cpp and c code <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0"> <assemblyIdentity version="4.0" processorArchitecture="X7460" name="myproject" type="win32"/> <description>myproject Problem</description>  <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2"> <security> <requestedPrivileges> <requestedExecutionLevel level="requireAdministrator" uiAccess="false"/> </requestedPrivileges> </security> </trustInfo> </assembly> then i added this line of code in Resourcefile(.rc).Means one header file is there(Myproject.h).I added the line of code there #define MANIFEST_RESOURCE_ID 1 MANIFEST_RESOURCE_ID RT_MANIFEST "myproject.exe.manifest" Finally i did the following step Under Project, select Properties. 3. In Properties, select Manifest Tool, and then select Input and Output. 4. Add in the name of your application manifest file under Additional manifest files. 5. Rebuild your application. But i am getting lot of Syntax errors Is there any problems in the way which i followed.If i commented the line #define MANIFEST_RESOURCE_ID 1 MANIFEST_RESOURCE_ID RT_MANIFEST "myproject.exe.manifest" which added in Myproject.h for adding values in .rc file there willnot any error other than this general error c1010070: Failed to load and parse the manifest. The system cannot find the file specified. .\myproject.exe.manifest How to enable UAC prompt through programming

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Multiple choice test GUI with serialization of Q&A

- by Bobby

I'm working on a project for school in Java programming. I need to design a GUI that will take in questions and answers and store them in a file. It should be able to contain an unlimited number of questions. We have covered binary I/O. How do I write the input they give to a file? How would I go about having them add multiple questions from this GUI? package multiplechoice; import java.awt.*; import javax.swing.*; public class MultipleChoice extends JFrame { public MultipleChoice() { /* * Setting Layout */ setLayout(new GridLayout(10,10)); /* * First Question */ add(new JLabel("What is the category of the question?: ")); JTextField category = new JTextField(); add(category); add(new JLabel("Please enter the question you wish to ask: ")); JTextField question = new JTextField(); add(question); add(new JLabel("Please enter the correct answer: ")); JTextField correctAnswer = new JTextField(); add(correctAnswer); add(new JLabel("Please enter a reccomended answer to display: ")); JTextField reccomendedAnswer = new JTextField(); add(reccomendedAnswer); add(new JLabel("Please enter a choice for multiple choice option " + "A")); JTextField A = new JTextField(); add(A); add(new JLabel("Please enter a choice for multiple choice option " + "B")); JTextField B = new JTextField(); add(B); add(new JLabel("Please enter a choice for multiple choice option " + "C")); JTextField C = new JTextField(); add(C); add(new JLabel("Please enter a choice for multiple choice option " + "D")); JTextField D = new JTextField(); add(D); add(new JButton("Compile Questions")); add(new JButton("Next Question")); } public static void main(String[] args) { /* * Creating JFrame to contain questions */ FinalProject frame = new FinalProject(); // FileOutputStream output = new FileOutputStream("Questions.dat"); JPanel panel = new JPanel(); // button.setLayout(); // frame.add(panel); panel.setSize(100,100); // button.setPreferredSize(new Dimension(100,100)); frame.setTitle("FinalProject"); frame.setSize(600, 400); frame.setLocationRelativeTo(null); // Center the frame frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); } }

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Can I use this Ajax script to communicate and exchange data between client and server?

- by lala

This block of code is for client.html (it is located in this www.client.com/client.html) - client side. The I have the code below that goes something like this: ajaxRequest.open("GET", "http://www.server.com/ajax.php", true); This is how I call the file ajax.php located in the server. Unfortunately I have no luck at all. It cannot connect to the server I'm calling. BTW, the ips /test site I've been using are all no restrictions, and is accessible to all. However, I tried to simulate by putting both client.html and ajax.php in same site and it works well. So my question is does this script works only if you are in same site? or does it work also in client-server scenario? What else do I have to do in order to make this work? //client.html <script language="javascript" type="text/javascript">  </script> <form name='myForm'> Name: <input type='text' onChange="ajaxFunction();" name='username' /> <br /> Time: <input type='text' name='time' /> </form> </body> </html> // ajax.php <?php echo date("H:i:s"); ?>

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ASP.NET MVC 3 NOT showing appropriate view, action called using jquery

- by TunAntun

I have a small problem. My action is : public ViewResult SearchForRooms(int HotelDDL) { List<Room> roomsInHotel = bl.ReturnRoomsPerHotel(HotelDDL); return View(roomsInHotel); } Here is the jquery that is calling the action: <script type="text/javascript" language="javascript"> $(document).ready(function () { $("#HotelDDL").change(function () { var text = $("#HotelDDL option:selected").text(); var value = $("#HotelDDL option:selected").val(); alert("Selected text=" + text + " Selected value= " + value); $.post("/Home/SearchForRooms", { HotelDDL: $("#HotelDDL option:selected").val() }); }); }); </script> And finally, here is the View that should be called: @model IEnumerable<RoomReservation.Entities.Entities.Room> @{ ViewBag.Title = "Search"; } <h2>Result</h2> <table> <tr> <th> City </th> <th> Hotel </th> <th> Room label </th> <th> Number of beds </th> <th> Price per night </th> <th></th> </tr> @foreach (var item in Model) { <tr> <td> @Html.DisplayFor(modelitem=>item.Hotel.City.Name) </td> <td> @Html.DisplayFor(modelItem => item.Hotel.Name) </td> <td> @Html.DisplayFor(modelItem => item.Name) </td> <td> @Html.DisplayFor(modelItem => item.NumberOfBeds) </td> <td> @Html.DisplayFor(modelItem => item.PricePerNight) </td> </tr> } </table> Everthing is working ok (databse return all rooms correctly) except final view rendering. I have tried Phil's tool but it doesn't give me any suspicious hints: RouteDebug.RouteDebugger.RewriteRoutesForTesting(RouteTable.Routes); So, why is it not showing after jscript send it's post method to SearchForRooms()? Thank you P.S. If you need any other piece of code please just say so.

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How do I access the enumerated item with an indexer and assign array string to it for display?

- by g00p3k

EDITED: Updated 3/23/09. See rest of post at bottom. I'm still having trouble with the indexer. Anymore help or examples would really help me out. Write a class, MyCourses, that contains an enumeration of all the courses that you are currently taking. This enum should be nested inside of your class MyCourses. Your class should also have an array field that provides a short description (as a String) of each of your courses. Write an indexer that takes one of your enumerated courses as an index and returns the String description of the course. Write a class MyFriends that contains an indexer that provides access to the names of your friends. namespace IT274_Unit4Project { public class MyCourses { // enumeration that contains an enumeration of all the courses that // student is currently enrolled in public enum CourseName {IT274= 0,CS210 = 1} // array field that provides short description for each of classes, // returns string description of the course private String[] courseDescription = {"Intermediate C#: Teaches intermediate elements of C# programming and software design", "Career Development Strategies: Teaches principles for career progression, resume preparation, and overall self anaylsis"}; // indexer that takes one of the enumerated courses as an index // and returns the String description of the course public String this[CourseName index] { get { if (index == 1) return courseDescription[0]; else return courseDescription[1]; } set { if (index == 1) courseDescription[0] = value; else courseDescription[1] = value; } } } }//end public class MyCourses I'm working on this homework project and having trouble understanding the text explaining how to correctly take the accessed value of the enumeration and then apply the string array value to it. Can you please help me understand this? The text we are using is very difficult and poorly written for a beginner to understand, so I'm kind of on my own here. I've got the first parts written, but need some help on the accessing of the enumeration value and assigning, i think i'm close, but don't understand how to properly get and set the values on this. Please do not provide me with direct code answers, unless a MSDN style explanation that is generalized and not specific to my project. ie: public class MyClass { string field1; string field2; //properties public string Value1 get etc... Thanks!

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Copy image to BLOB from client pc aka Java function in Oracle

- by mumich

Hi guys, I've been stuck with this for past two days. I've go java function stored in Oracle system which is supposed to copy image from local drive do remote database and store it in BLOB - it's called CopyBLOB and looks like this: import java.sql.*; import oracle.sql.*; import java.io.*; public class CopyBLOB { static int id; static String fileName = null; static Connection conn = null; public CopyBLOB(int idz, String f) { id = idz; fileName = f; } public static void copy(int ident, String path) throws SQLException, FileNotFoundException { CopyBLOB cpB = new CopyBLOB(ident, path); cpB.getConnection(); cpB.callUpdate(id, fileName); } public void getConnection() throws SQLException { DriverManager.registerDriver (new oracle.jdbc.OracleDriver()); try { conn = DriverManager.getConnection("jdbc:oracle:thin:@oraserv.ms.mff.cuni.cz:1521:db", "xxx", "xxx"); } catch (SQLException sqlex) { System.out.println("SQLException while getting db connection: "+sqlex); if (conn != null) conn.close(); } catch (Exception ex) { System.out.println("Exception while getting db connection: "+ex); if (conn != null) conn.close(); } } public void callUpdate(int id, String file ) throws SQLException, FileNotFoundException { CallableStatement cs = null; try { conn.setAutoCommit(false); File f = new File(file); FileInputStream fin = new FileInputStream(f); cs = (CallableStatement) conn.prepareCall( "begin add_image(?,?); end;" ); cs.setInt(1, id ); cs.setBinaryStream(2, fin, (int) f.length()); cs.execute(); conn.setAutoCommit(true); } catch ( SQLException sqlex ) { System.out.println("SQLException in callUpdateUsingStream method of given status : " + sqlex.getMessage() ); } catch ( FileNotFoundException fnex ) { System.out.println("FileNotFoundException in callUpdateUsingStream method of given status : " + fnex.getMessage() ); } finally { try { if (cs != null) cs.close(); if (conn != null) conn.close(); } catch ( Exception ex ) { System.out.println("Some exception in callUpdateUsingStream method of given status : " + ex.getMessage( ) ); } } } } The wrapper function is defined in package "MyPackage" as folows: procedure image_adder( id varchar2, path varchar2 ) AS language java name 'CopyBLOB.copy(java.lang.String, java.lang.String)'; And the inserting function called image_add is as simple as this: procedure add_image( id numeric(10), pic blob) AS BEGIN insert into pictures values (seq_pic.nextval, id, pic); END add_image; Now the problem: When I type call MyPackage.image_adder(1, 'd:\samples\img.jpg'); I get the ORA-29531 Error: No method copy in class CopyBLOB. Can you help me, please?

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Linux termios VTIME not working?

- by San Jacinto

We've been bashing our heads off of this one all morning. We've got some serial lines setup between an embedded linux device and an Ubuntu box. Our reads are getting screwed up because our code usually returns two (sometimes more, sometimes exactly one) message reads instead of one message read per actual message sent. Here is the code that opens the serial port. InterCharTime is set to 4. void COMBaseClass::OpenPort() { cerr<< "openning port"<< port <<"\n"; struct termios newtio; this->fd = -1; int fdTemp; fdTemp = open( port, O_RDWR | O_NOCTTY); if (fdTemp < 0) { portOpen = 0; cerr<<"problem openning "<< port <<". Retrying"<<endl; usleep(1000000); return; } newtio.c_cflag = BaudRate | CS8 | CLOCAL | CREAD ;//| StopBits; newtio.c_iflag = IGNPAR; newtio.c_oflag = 0; /* set input mode (non-canonical, no echo,...) */ newtio.c_lflag = 0; newtio.c_cc[VTIME] = InterCharTime; /* inter-character timer in .1 secs */ newtio.c_cc[VMIN] = readBufferSize; /* blocking read until 1 char received */ tcflush(fdTemp, TCIFLUSH); tcsetattr(fdTemp,TCSANOW,&newtio); this->fd = fdTemp; portOpen = 1; } The other end is configured similarly for communication, and has one small section of particular iterest: while (1) { sprintf(out, "\r\nHello world %lu", ++ulCount); puts(out); WritePort((BYTE *)out, strlen(out)+1); sleep(2); } //while Now, when I run a read thread on the receiving machine, "hello world" is usually broken up over a couple messages. Here is some sample output: 1: Hello 2: world 1 3: Hello 4: world 2 5: Hello 6: world 3 where number followed by a colon is one message recieved. Can you see any error we are making? Thank you. Edit: For clarity, please view section 3.2 of this resource href="http://www.faqs.org/docs/Linux-HOWTO/Serial-Programming-HOWTO.html. To my understanding, with a VTIME of a couple seconds (meaning vtime is set anywhere between 10 and 50, trial-and-error), and a VMIN of 1, there should be no reason that the message is broken up over two separate messages.

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This code appears to achieve the return of a null reference in C++

- by Chuck

Hi folks, My C++ knowledge is somewhat piecemeal. I was reworking some code at work. I changed a function to return a reference to a type. Inside, I look up an object based on an identifier passed in, then return a reference to the object if found. Of course I ran into the issue of what to return if I don't find the object, and in looking around the web, many people claim that returning a "null reference" in C++ is impossible. Based on this advice, I tried the trick of returning a success/fail boolean, and making the object reference an out parameter. However, I ran into the roadblock of needing to initialize the references I would pass as actual parameters, and of course there is no way to do this. I retreated to the usual approach of just returning a pointer. I asked a colleague about it. He uses the following trick quite often, which is accepted by both a recent version of the Sun compiler and by gcc: MyType& someFunc(int id) { // successful case here: // ... // fail case: return *static_cast<MyType*>(0); } // Use: ... MyType& mt = somefunc(myIdNum); if (&mt) // test for "null reference" { // whatever } ... I have been maintaining this code base for a while, but I find that I don't have as much time to look up the small details about the language as I would like. I've been digging through my reference book but the answer to this one eludes me. Now, I had a C++ course a few years ago, and therein we emphasized that in C++ everything is types, so I try to keep that in mind when thinking things through. Deconstructing the expression: "*static_cast(0);", it indeed seems to me that we take a literal zero, cast it to a pointer to MyType (which makes it a null pointer), and then apply the dereferencing operator in the context of assigning to a reference type (the return type), which should give me a reference to the same object pointed to by the pointer. This sure looks like returning a null reference to me. Any advice in explaining why this works (or why it shouldn't) would be greatly appreciated. Thanks, Chuck

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Making an efficient algorithm

- by James P.

Here's my recent submission for the FB programming contest (qualifying round only requires to upload program output so source code doesn't matter). The objective is to find two squares that add up to a given value. I've left it as it is as an example. It does the job but is too slow for my liking. Here's the points that are obviously eating up time: List of squares is being recalculated for each call of getNumOfDoubleSquares(). This could be precalculated or extended when needed. Both squares are being checked for when it is only necessary to check for one (complements). There might be a more efficient way than a double-nested loop to find pairs. Other suggestions? Besides this particular problem, what do you look for when optimizing an algorithm? public static int getNumOfDoubleSquares( Integer target ){ int num = 0; ArrayList<Integer> squares = new ArrayList<Integer>(); ArrayList<Integer> found = new ArrayList<Integer>(); int squareValue = 0; for( int j=0; squareValue<=target; j++ ){ squares.add(j, squareValue); squareValue = (int)Math.pow(j+1,2); } int squareSum = 0; System.out.println( "Target=" + target ); for( int i = 0; i < squares.size(); i++ ){ int square1 = squares.get(i); for( int j = 0; j < squares.size(); j++ ){ int square2 = squares.get(j); squareSum = square1 + square2; if( squareSum == target && !found.contains( square1 ) && !found.contains( square2 ) ){ found.add(square1); found.add(square2); System.out.println( "Found !" + square1 +"+"+ square2 +"="+ squareSum); num++; } } } return num; }

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Google Map + MarkerClusterer only takes place when map completely zooms out

- by user415795

The clustering works but somehow it only takes place at the maximum zoom out(the largest view with all nations), the moment I zoom in by 1 value, the clustering icon changes back to markers. I try with all kinds of values on the maxZoom and gridSize clusterer options with no help. Can someone please kindly advice. Thanks. <script language="javascript" type="text/javascript"> var markersArray = []; var mc = null; var markersArray = []; var mc = null; var map; var mapOptions; var geocoder; var infoWindow; var http_request = false; var lat = 0; var lng = 0; var startingZoom = 7; var lowestZoom = 1; // The lower the number, the more places can be seen on within the bounds. var highestZoom = 8; function mapLoad() { geocoder = new google.maps.Geocoder(); infoWindow = new google.maps.InfoWindow(); mapOptions = { zoomControl: true, zoom: 2, minZoom: lowestZoom, maxzoom: highestZoom, draggable: true, scrollwheel: true, disableDoubleClickZoom: true, mapTypeId: google.maps.MapTypeId.ROADMAP }; map = new google.maps.Map(document.getElementById('map'), mapOptions); } $(document).ready(function () { var searchUrl; var locations; // Place the user's current location marker on the map var Location = new google.maps.LatLng(1.340319, 103.743744); var Location2 = new google.maps.LatLng(1.322347, 103.757881); createMarker('1', Location, 'My Location', '', '', '', '/Images/home.png'); createMarker('1', Location2, 'My Location', '', '', '', '/Images/bb.png'); var bounds = new google.maps.LatLngBounds(); bounds.extend(gameLocation); map.fitBounds(bounds); }); // Create the marker with address information function createMarker(actId, point, address1, address2, town, postcode, icon) { var marker = new google.maps.Marker({ map: map, icon: icon, position: point, title: address1, animation: google.maps.Animation.DROP }); marker.metadata = { id: actId }; markersArray.push(marker); mc = new MarkerClusterer(map, markersArray); return marker; } </script>

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Bug in Safari: options.length = 0; not working as expected in Safari 4

- by Stefan

This is not a real question, but rather an answer to save some others the hassle of tracking this nasty bug down. I wasted hours finding this out. When using options.length = 0; to reset all options of a select element in safari, you can get mixed results depending on wether you have the Web Inspector open or not. If the web inspector is open you use myElement.options.length = 0; and after that query the options.length(), you might get back 1 instead of 0 (expected) but only if the Web Inspector is open (which is often the case when debugging problem like this). Workaround: Close the Web Inspector or call myElement.options.length = 0; twice like so: myElement.options.length = 0; myElement.options.length = 0; Testcase: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>Testcase</title> <script type="text/javascript" language="javascript" charset="utf-8"> function test(el){ var el = document.getElementById("sel"); alert("Before calling options.length=" + el.options.length); el.options.length = 0; alert("After calling options.length=" + el.options.length); } </script> </head> <body onLoad="test();"> <p> Make note of the numbers displayed in the Alert Dialog, then open Web inspector, reload this page and compare the numbers. </p> <select id="sel" multiple> <option label="a----------" value="a"></option> <option label="b----------" value="b"></option> <option label="c----------" value="c"></option> </select> </body> </html>

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Why won't my images align properly?

I'm trying to make a dynamically sizable title banner, using fairly simple image tricks. I place the banner image in a table cell, and set the background-image of the table row to a one-pixel-wide repeat of the banner's right-most pixel column. Thus, the banner image appears to stretch to fit the screen width without stretching the logo. The code below is my entire page so far, and the problem is shown in a red circle in the screenshot. This is the transition where the main image ends and the one-pixel-wide background image begins. It appears that the one-pixel-wide bar at the end is compressed by one pixel - making the tops align properly, while the bottoms are one pixel off. I should add that I have checked the images more than once to make cure they the image data is correct. They are %100 accurate as far as MSPaint is concerned. <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title></title> </head> <body bgcolor="#000000"> <form id="form1" runat="server"> <div> <table style="width:100%; "> <tr style="background-image: url('Images/Banners/WebBannerWideBar.png')">  <td> <img alt="Angry Octopus" src="Images/Banners/WebBannerWide.png" />  </td> </tr> </table> </div> </form> </body> </html>

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How should I ethically approach user password storage for later plaintext retrieval?

- by Shane

As I continue to build more and more websites and web applications I am often asked to store user's passwords in a way that they can be retrieved if/when the user has an issue (either to email a forgotten password link, walk them through over the phone, etc.) When I can I fight bitterly against this practice and I do a lot of ‘extra’ programming to make password resets and administrative assistance possible without storing their actual password. When I can’t fight it (or can’t win) then I always encode the password in some way so that it at least isn’t stored as plaintext in the database—though I am aware that if my DB gets hacked that it won’t take much for the culprit to crack the passwords as well—so that makes me uncomfortable. In a perfect world folks would update passwords frequently and not duplicate them across many different sites—unfortunately I know MANY people that have the same work/home/email/bank password, and have even freely given it to me when they need assistance. I don’t want to be the one responsible for their financial demise if my DB security procedures fail for some reason. Morally and ethically I feel responsible for protecting what can be, for some users, their livelihood even if they are treating it with much less respect. I am certain that there are many avenues to approach and arguments to be made for salting hashes and different encoding options, but is there a single ‘best practice’ when you have to store them? In almost all cases I am using PHP and MySQL if that makes any difference in the way I should handle the specifics. Additional Information for Bounty I want to clarify that I know this is not something you want to have to do and that in most cases refusal to do so is best. I am, however, not looking for a lecture on the merits of taking this approach I am looking for the best steps to take if you do take this approach. In a note below I made the point that websites geared largely toward the elderly, mentally challenged, or very young can become confusing for people when they are asked to perform a secure password recovery routine. Though we may find it simple and mundane in those cases some users need the extra assistance of either having a service tech help them into the system or having it emailed/displayed directly to them. In such systems the attrition rate from these demographics could hobble the application if users were not given this level of access assistance, so please answer with such a setup in mind. Thanks to Everyone This has been a fun questions with lots of debate and I have enjoyed it. In the end I selected an answer that both retains password security (I will not have to keep plain text or recoverable passwords), but also makes it possible for the user base I specified to log into a system without the major drawbacks I have found from normal password recovery. As always there were about 5 answers that I would like to have marked correct for different reasons, but I had to choose the best one--all the rest got a +1. Thanks everyone!

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Jquery ajax using asp.net does not work on IE9 during the 2nd call of the function?

- by randelramirez1

I have gridview that is loaded from another aspx page after an ajax call, the problem is it works on chrome/firefox/safari but using ie9 the ajax call would work fine during the first call but when i try to call the function again it throws an 304 status on the network tab of ie9 dev tool and the gridview is not refreshed. Here is the jquery code: <%@ Page Language="C#" AutoEventWireup="true" CodeFile="LoadCoursesGridViewHere.aspx.cs" Inherits="CoursesGridView" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title></title> <script src="Scripts/jquery-1.8.2.js" type="text/javascript"></script> </head> <body> <form id="form1" runat="server"> <div id="Gridview-container"> <asp:GridView ID="GridView1" runat="server"> </asp:GridView> </div> <asp:TextBox ID="TextBox1" runat="server" ViewStateMode="Disabled"></asp:TextBox> <%-- <asp:Button Text="text" ID="btn" OnClientClick=" __doPostBack('UpdatePanel1', '')" runat="server" />--%> <input type="button" id="btn" value="insert"/> </form> <script type="text/javascript"> $("#btn").click(function () { var a = $("#TextBox1").val(); $.ajax({ url: 'WebService.asmx/insert', data: "{ 'name': '" + a + "' }", contentType: "application/json; charset=utf-8", type: "POST", success: function () { // alert('insert was performed.'); $("#Gridview-container").empty(); $("#Gridview-container").load("GridViewCourses.aspx #GridView1"); } }); }); </script> </body> </html> What happen is that after click the button it will insert the textbox value in the database through the webservice 'insert' and then reload the gridview that is placed inside a different aspx page. The problem is that when I ran it on IE9 during the 1st insert everything works properly but the succeeding inserts does reload the gridview and I noticed that it says '304' on the network tab of ie9 dev tool.

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Realtime MySQL search results on an advanced search page

- by Andrew Heath

I'm a hobbyist, and started learning PHP last September solely to build a hobby website that I had always wished and dreamed another more competent person might make. I enjoy programming, but I have little free time and enjoy a wide range of other interests and activities. I feel learning PHP alone can probably allow me to create 98% of the desired features for my site, but that last 2% is awfully appealing: The most powerful tool of the site is an advanced search page that picks through a 1000+ record game scenario database. Users can data-mine to tremendous depths - this advanced page has upwards of 50 different potential variables. It's designed to allow the hardcore user to search on almost any possible combination of data in our database and it works well. Those who aren't interested in wading through the sea of options may use the Basic Search, which is comprised of the most popular parts of the Advanced search. Because the advanced search is so comprehensive, and because the database is rather small (less than 1,200 potential hits maximum), with each variable you choose to include the likelihood of getting any qualifying results at all drops dramatically. In my fantasy land where I can wield AJAX as if it were Excalibur, my users would have a realtime Total Results counter in the corner of their screen as they used this page, which would automatically update its query structure and report how many results will be displayed with the addition of each variable. In this way it would be effortless to know just how many variables are enough, and when you've gone and added one that zeroes out the results set. A somewhat similar implementation, at least visually, would be the Subtotal sidebar when building a new custom computer on IBuyPower.com For those of you actually still reading this, my question is really rather simple: Given the time & ability constraints outlined above, would I be able to learn just enough AJAX (or whatever) needed to pull this one feature off without too much trouble? would I be able to more or less drop-in a pre-written code snippet and tweak to fit? or should I consider opening my code up to a trusted & capable individual in the future for this implementation? (assuming I can find one...) Thank you.

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Java Flow Control Problem

- by Kyle_Solo

I am programming a simple 2d game engine. I've decided how I'd like the engine to function: it will be composed of objects containing "events" that my main game loop will trigger when appropriate. A little more about the structure: Every GameObject has an updateEvent method. objectList is a list of all the objects that will receive update events. Only objects on this list have their updateEvent method called by the game loop. I’m trying to implement this method in the GameObject class (This specification is what I’d like the method to achieve): /** * This method removes a GameObject from objectList. The GameObject * should immediately stop executing code, that is, absolutely no more * code inside update events will be executed for the removed game object. * If necessary, control should transfer to the game loop. * @param go The GameObject to be removed */ public void remove(GameObject go) So if an object tries to remove itself inside of an update event, control should transfer back to the game engine: public void updateEvent() { //object's update event remove(this); System.out.println("Should never reach here!"); } Here’s what I have so far. It works, but the more I read about using exceptions for flow control the less I like it, so I want to see if there are alternatives. Remove Method public void remove(GameObject go) { //add to removedList //flag as removed //throw an exception if removing self from inside an updateEvent } Game Loop for(GameObject go : objectList) { try { if (!go.removed) { go.updateEvent(); } else { //object is scheduled to be removed, do nothing } } catch(ObjectRemovedException e) { //control has been transferred back to the game loop //no need to do anything here } } // now remove the objects that are in removedList from objectList 2 questions: Am I correct in assuming that the only way to implement the stop-right-away part of the remove method as described above is by throwing a custom exception and catching it in the game loop? (I know, using exceptions for flow control is like goto, which is bad. I just can’t think of another way to do what I want!) For the removal from the list itself, it is possible for one object to remove one that is farther down on the list. Currently I’m checking a removed flag before executing any code, and at the end of each pass removing the objects to avoid concurrent modification. Is there a better, preferably instant/non-polling way to do this?

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Redirecting users in JSP from within a includes - java syntax error

- by Mark Hazlett

Hey everyone, So my setup for my web application is that I have a general header and footer and then I just include them in all my other pages so that all the common elements for all the pages are in a single page. The only problem I'm running into is when I want to redirect the user back to a login page if the "username" session has not already been created. The problem that I"m running into is that I have an if statement at the top of my header.jsp and then I have the else in the footer.jsp and it is giving me a java syntax error. Any ideas? Here is the code I'm referring to... <%@page contentType="text/html" pageEncoding="UTF-8"%> <% if(session.getAttribute("username") != null) { %> <%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">  <link rel="stylesheet" href="../CSS/headerStyle.css" type="text/css" media="screen" /> <title>Insert title here</title> </head> <body> <div id="container"> <div id="header"> <div id="headerTitle">Title</div> </div> </div> <%} %> And then here is the footer <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <link rel="stylesheet" href="../CSS/headerStyle.css" type="text/css" media="screen" /> </head> <body> <div id="footer"></div> </body> </html> <% else { response.sendRedirect("../wa_login/login.jsp"); } %> However it is giving me an error on the else statement because the else doesn't have an if statement because it's in the header file.

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.Net Custom Components "disappear" after file save

- by EatATaco

I might have a hard time explaining this because I am at a total loss for what is happening so I am just looking for some guidance. I might be a bit wordy because I don't know exactly what is the relevant information. I am developing a GUI for a project that I am working on in using .Net (C#) Part of the interface mimics, exactly, what we do in another product. For consistency reasons, my boss wants me to make it look the same way. So I got the other software and basically copied and pasted the components into my new GUI. This required me to introduce a component library (the now defunct Graphics Server GSNet, so I can't go to them for help) so I could implement some simple graphs and temperature/pressure "widgets." The components show up fine, and when I compile, everything seems to work fine. However, at some point during my programming it just breaks. Sometimes the tab that these components are on starts throwing exceptions when I view the designer page (A missing method exception) so it won't display. Sometimes JUST those components from the GSNet library don't show up. Sometimes, if I try to run it, I get a not-instantiated exception on one of their lines of code in the designer code file. Sometimes I can't view the designer at all. No matter what I do I can't reverse it. Even if I undo what I just did it won't fix it. If it happens, I have to revert to a backup and start over again. So I started to backup pretty much every step. I compile it and it works. I comment out a line of code, save it, and then uncomment that same line of code (so I am working with the same exact code) and the components all disappear. It doesn't matter what line of code I actually comment out, as long as it is in the same project that these components are being used. I pretty much have to use the components. . . so does anyone have any suggestion or where I can look to debug this?

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How can I sort an array, yet exclude certain elements (to be kept at the same position in the array)

- by calumbrodie

This will be implemented in Javascript (jQuery) but I suppose the method could be used in any language. I have an array of items and I need to perform a sort. However there are some items in the array that have to be kept in the same position (same index). The array in question is build from a list of <li> elements and I'm using .data() values attached to the list item as the value on which to sort. What approach would be best here? <ul id="fruit"> <li class="stay">bananas</li> <li>oranges</li> <li>pears</li> <li>apples</li> <li class="stay">grapes</li> <li>pineapples</li> </ul> <script type="text/javascript"> var sugarcontent = new Array('32','21','11','45','8','99'); $('#fruit li').each(function(i,e){ $(this).data(sugarcontent[i]); }) </script> I want the list sorted with the following result... <ul id="fruit"> <li class="stay">bananas</li>  <li>pineapples</li>  <li>apples</li>  <li>oranges</li>  <li class="stay">grapes</li>  <li>pears</li>  </ul> Thanks!

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Windows MAchine Debugging

- by PrettyFlower

I've been learning how to program for Windows for some time now and am getting pretty comfy with COM. I had thought to go over to Linux and do some C++ programming there and I wished to run Rosetta Commons so I installed Fedora. I had tried installing Ubuntu a few months ago and things got messy. I had a glitch, maybe caused by one of the live cd creators, my video card or something I don't know. Who Crashed suggested it was my video card and I had regular messages about ntfs.sys and page file issues. At any rate I just installed Fedora and the same thing is happening again. I would like to think with the twenty five years of doing this that I might finally make some headway into debugging my system. I think I may have overlooked a lot of what could be done in favor of simply uninstalling, reinstalling and formatting and starting from scratch. I have opened up the folder windows debugging tools, quite accidentally and just before I was going to clean sweep again, and I found KD and WinDbg. I had never seen these before and I felt that maybe I should look into this. I am quite familiar with the modern machine that is known as the computer, I know what a Kernel is and am now pretty familiar with at the very least Windows Operating System Services. I wish to begin tracking my own machines errors. I understand that most kernel debugging is done on a second machine but I don't have one. And also I understand the goal of the debugger seems to be less about run of the mill errors and more about development time strategies but I'm sure there is more to this. This is my first go at this and I thought maybe I could get some suggestions on where to go from here. I would really like to learn ways to fix my machine and also maybe pick up some tricks on the dev side as well. I hope this isn't too broad a question or too generalized. I'm really just looking for the keywords and an overview of the more routine strategies used. thx

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